Electrical submersible pumps (ESP) are widely used to pump oil production wells. A typical ESP has a rotary pump driven by an electrical motor. A seal section is located between the pump and the motor to reduce the differential between the well fluid pressure on the exterior of the motor and the lubricant pressure within the motor. A drive shaft, normally in several sections, extends from the motor through the seal section and into the pump for rotating the pump. The pump may be a centrifugal pump having a large number of stages, each stage having an impeller and diffuser. The pump may alternately be a progressing cavity pump having a metal rotor with a helical exterior rotated within an elastomeric stator having a double helical interior.
The pump assembly is much longer than its diameter. Shaft or radial bearings are located in the various modules of the pump assembly to support the shaft radially. The radial bearing has a bearing sleeve that is secured by a key to the shaft for rotation therewith. A non rotating bushing has a bore that closely receives the bearing sleeve in rotating, sliding engagement. The bushing is secured in a member that serves as a bearing carrier. In the pump and seal section, the bearing carrier may be secured by a threaded connection to the housing. The bushing may be press-fit into a bore of the bearing carrier. In the motor, the bearing carrier may be an annular member that has elastomeric rings on the exterior. The elastomeric rings frictionally engage an inner diameter of the motor stator to prevent rotation of the bearing carrier.
In some cases, the bushing may be formed of a more wear resistant material, such as tungsten carbide, than the bearing carrier. The wear resistant material is particularly employed for abrasive well fluid applications. It the hard metal bushing is press-fit into the bearing carrier, damage may occur. The wear resistant bushing may misalign slightly when pressed into the bearing carrier. Also, thermal expansion differences between the wear resistant bushing and the bearing carrier may create problems.